Conventional radio receiver architecture is frequency band-specific due to performance limitations in the radio-frequency (RF) front-end hardware components. Multiband receivers are generally implemented by using multiple parallel radio-frequency analog-to-digital converter (RF-ADC) branches per receiver (Rx) branch.
FIG. 1 shows a conventional multiband radio receiver super-heterodyne architecture 100 known in the art. An RF front-end hardware unit 110 including an antenna 112 provides an input signal 108 to a plurality of RF-ADC branches 102,104,106. Each RF-ADC branch 102,104,106 includes an RF front-end filter 114, a low-noise amplifier (LNA) 116, a first mixer 118 receiving local oscillator input from a first local oscillator (LO) 120, an image-reject filter 122, a second mixer 124 receiving input from a second LO 126, a channel-select filter 128, and an analog-to-digital converter (ADC) 130.
However, once the number of receiver branches becomes very large, such as in a massive-multiple-input multiple-output (M-MIMO) configuration (e.g. 64+Rx branches), this conventional architecture may encounter problems of scalability and cost-effectiveness. It might be difficult to design a single, frequency-agnostic multiband radio device based on this conventional architecture covering a large RF range, such as the sub-6 GHz RF range: within the sub-6 GHz range, there are many possible multiband combinations, and the conventional architecture may not be able to flexibly support all these multiband combinations through software configuration using the same hardware.
A phalanx radio architecture has been disclosed which achieves multiband aggregation for applications such as cell tower antennas: US Patent Application Publication US 2016/0021552 A1, “Phalanx Radio System Architecture for High Capacity Wireless Communication”, filed Jul. 17, 2014, hereby incorporated by reference in its entirety.
An example of the disclosed phalanx radio architecture 200 is shown in FIG. 2. Each Rx branch 204 includes band-pass filter block 209 consisting of one band pass filter per band in the multiband input signal. The output of these branches 204 is combined by a combiner 212, which provides the combined signal 214 to a high speed ADC 216 clocked by a clock unit 218 to produce a combined digital output signal 220. In this example architecture 200, the band-pass filters 209 are band-specific for each branch 204: they are not frequency band-agnostic.
However, the previously disclosed phalanx radio architecture is limited to preconfigured multiband combinations, and may not be sufficiently flexible to support a large number of multiband combinations. FIG. 3 shows an example of the operation of the previously disclosed phalanx radio architecture 200. The signals received by four Rx branches 302,304,306,308 are shown, both before 310 and after 312 processing by the band-select and packing processes of each Rx branch 302,304,306,308. On the right at input frequency range 310, the pre-processed signals are shown to each have three frequency bands 320,322,324 of interest that overlap for each of the four branches 302,304,306,308. The frequency of each LO 330,332,334,336 corresponding to each of the four branches 302,304,306,308 is also shown in range 310.
After being processed by the band-select and packing process, these bands of interest 320,322,324 are re-centered within the left range 312 in non-overlapping frequencies. When combined by the combiner 212 into combined signal 214, these bands 320,322,324 from each of the four branches 302,304,306,308 are encoded in the combined signal 214 at non-overlapping frequencies.
However, this aggregation method requires that the bands 320,322,324 have specific bandwidths (BW) and specific frequency gaps between them in order to effectively combine them into the combined signal 214. The number of multiband combinations this method and architecture can support may therefore be limited.